1. Field of the Invention
The present invention relates generally to a display device and more particularly to a color filtering member in the display device.
2. Description of the Related Art
An LCD apparatus generally includes an array substrate, a color filter substrate, and liquid crystals interposed between the array substrate and the color filter substrate. The liquid crystals have an anisotropic dielectric constant such that the LCD apparatus can display images by in response to variations in the electric field that is applied to the liquid crystals. The liquid crystals transmit different amounts of light depending on the intensity of the applied electric field.
LCD apparatus can generally be classified into three types: 1) a reflective type LCD apparatus that uses an external light, 2) a transmissive type LCD apparatus that uses an internal light, and 3) a trans-reflective type LCD apparatus that uses both external and internal lights.
FIG. 1 is a cross-sectional view showing a conventional transreflective type LCD apparatus.
Referring to FIG. 1, the conventional transreflective type LCD includes an array substrate 110, a color filter substrate 190 and liquid crystal interposed between the array substrate 110 and the color filter substrate 190.
The array substrate 110 includes a thin film transistor 120 formed on a surface of the array substrate 110. The color filter substrate 190 includes a common electrode 180.
The thin film transistor 120 includes a gate electrode 122, gate-insulation layers 123 and 124, an active pattern 125, a source electrode 126 and a drain electrode 127.
A transparent material, such as an acrylic organic layer 130, is formed on the thin film transistor 120 and the array substrate 140 with a predetermined thickness. In order to improve the brightness of the device, a surface of the acrylic organic layer 130 (e.g., the upper surface as shown in FIG. 1) is patterned to enhance diffusion of light. For example, the surface may be formed with concave and/or convex portions. Also, the acrylic organic layer 130 has an opening that exposes the drain electrode 127.
A transmissive electrode 140 for transmitting internal light and a reflective electrode 160 for reflecting external light are successively formed on the acrylic organic layer 130. An insulating layer 150 is formed between the transmissive electrode 140 and the reflective electrode 160. The reflective electrode 160 and the insulating layer 150 are deposited discontinuously to form an opening 165 through which internal light is transmitted. The transmissive electrode 140 typically includes ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide), and the reflective electrode 160 typically includes aluminum or aluminum-neodymium alloy.
The color filter substrate 190 having the common electrode 180 is disposed on the array substrate 110 and the liquid crystal 170 is positioned between the array substrate 110 and the color filter substrate 190 to form a transreflective type LCD.
Popular uses for LCDs include portable or handheld applications. While handheld applications generally require low power consumption due to their reliance on batteries as the power source, it is also desirable to provide high brightness, which increases power consumption. In order to satisfy these two demands that conflict with each other, a new method of lowering power consumption without sacrificing brightness level is desired.
Various methods have been adopted in an attempt to enhance brightness without significantly increasing power consumption. For example, the number of lamps or optical sheets that are used with an internal light source have been increased, the twist angle of liquid crystals has been varied, and black matrix has been removed from the color filter substrate. A black matrix is a light-shielding film that is typically positioned between different-colored pixels to keep the colors dearly separated. However, these methods tend to be accompanied by one or more undesirable side effects, such as an increased cost of manufacture or lowered contrast ratio, both of which adversely affect the reliability of an LCD apparatus.
FIG. 2 is a cross-sectional view of a currently available color filter substrate that does not include black matrix. The color filter substrate 200 of FIG. 2 includes an intercepting region 220, such as a black matrix, and a color filter 230 having R, G and B color filters 232a, 234a and 236a. The intercepting region 220 is formed on an area surrounding a display area, which is where the R, G and B color filters 232a, 234a and 236a are formed. While the intercepting regions that are typically located between the R, G and B color filters 232a, 234a and 236a are removed from the color filter substrate 200, the effect of the intercepting regions is achieved by partially overlapping the R, G and B color filter 232a, 234a and 236a that are adjacent to each other. The overlapped portions of the color filters function as the black matrix, thereby improving the brightness of the LCD apparatus.
The color filter substrate 200 includes a planarizing layer 240 formed on the color filter 230 to provide a substantially flat surface. The planarizing layer 240 is needed partly because the surface formed by the partially-overlapping color filters is more rugged than what is desirable for formation of the common electrode 250. Once a desired level of flatness is achieved by deposition of the planarizing layer 240, a common electrode 250 formed on the planarizing layer 240. A spacer 262 is formed on the common electrode 250 for maintaining a uniform colorless gap between the color filter substrate 200 and an array substrate 110 (see FIG. 1) when the two substrates are combined.
As shown in FIG. 2, however, the planarizing layer 240 does not provide an even surface that is desired for deposition of the common electrode 250. When the color filter substrate 200 having a non-flat surface is assembled into an LCD apparatus, light tends to leak through the sloped portions of the common electrode 250, reducing the brightness level. In order to achieve the goal of improving brightness without a significant increase in the power consumption level, methods are needed to minimize this light leakage.